Protein - what you should know!
by Dr Nerida Richards
Protein is an essential nutrient and after water, is the most plentiful substance in a horse’s body. Proteins form part of the hoof, hair, skin, organ tissue, muscles, eyes, blood and bones. They are also a crucial part of enzymes and hormones in the body. Protein molecules are made from building blocks called amino acids. Amino acids are small structures containing carbon, nitrogen, oxygen and hydrogen atoms and some contain sulphur.
There are approximately 20 known amino acids which can are joined or bonded together in almost limitless combinations to form proteins. Ten of these amino acids can be manufactured by the horse in its body, so they are known as non-essential amino acids. The remaining 10 amino acids are termed ESSENTIAL amino acids. These essential amino acids cannot be manufactured by the horse and must be supplied by the diet.
Protein quality is determined by how well it meets a horse’s requirement for amino acids, and particularly the essential amino acids. Different vegetable proteins contain different levels of the essential amino acids and thus vary in ‘quality’. Soybean contains the highest concentrations of many of the essential amino acids and is thus touted as the best quality vegetable protein available. Of particular note is that it contains high concentrations of Lysine and Threonine, which are thought to be the first and second limiting amino acids for horses.
The graph above compares the essential amino acid profile of full fat soybean to cottonseed meal. While both of these protein sources contain the same amount of protein (36% – 37%), the essential amino acid profile is very different. The low levels of lysine and threonine in cottonseed meal will slow growth and won’t facilitate the same level of muscle development as full fat soybean.
The Take Home Message Not all protein is the same. While two feeds may contain the same amount of crude protein, the levels of essential amino acids may vary, meaning one will be more beneficial to the horses than the other. When comparing feeds, look at the crude protein level, but also look at the specified ingredients to gauge the quality of that protein. Feeds containing soybean as their protein base will be of higher quality than feeds containing cottonseed meal or other similar vegetable protein meals
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